Gas-phase interactions between lead(II) ions and thiouracil nucleobases: A combined experimental and theoretical study

Abstract

The gas-phase interactions between lead(II) ions and 2-thiouracil, 4-thiouracil, and 2,4-dithiouracil have been investigated by combining mass spectrometry and theoretical calculations. The most abundant complexes observed, namely [Pb(thiouracil) Ϫ H] ϩ , have been studied by MS/MS experiments. Cationization by the metal allows an unambiguous characterization of the sulfur position, several fragment ions being specific of each isomer. Moreover, compared with the uracil fragmentation, new fragmentation channels are observed: elimination of PbS or total reduction of the metal. Calculations performed on the different structures, including tautomers, show that sulfur is the preferred complexation site, suggesting the greater affinity of lead for sulfur. The most stable structures are always preferentially bidentate. Natural population analysis indicates a charge transfer from the base to the metal with a more pronounced covalent character for sulfur compared to oxygen. Energetic profiles associated with the main fragmentations have been described. (J Am Soc Mass Spectrom 2009, 20, 359 -369)

Gas‐Phase Interactions between Lead(II) Ions and Cytosine: Tandem Mass Spectrometry and Infrared Multiple‐Photon Dissociation Spectroscopy Study

“…The first one, already encountered with uracil, thymine, and 4-thiouracil, [10,11] corresponds to the formation of [Pb,N,C,O] + (m/z 250). The first one, already encountered with uracil, thymine, and 4-thiouracil, [10,11] corresponds to the formation of [Pb,N,C,O] + (m/z 250).…”

“…The first one, already encountered with uracil, thymine, and 4-thiouracil, [10,11] corresponds to the formation of [Pb,N,C,O] + (m/z 250). [6,10,11,40,41] These two fragment ions further dissociate to generate the bare Pb + ion (m/z 208). [6,10,11,40,41] These two fragment ions further dissociate to generate the bare Pb + ion (m/z 208).…”

“…[5,6] Lead is another metal for which its toxicity is well known and its health damages are well established. [10,11] Besides structural study of the complexes, our main interest was to explore the different pathways that could account for the fragmentation observed in the MS/MS spectra. [7][8][9] Recently, we used MS/MS experiments and theoretical calculations to study the reactivity of thymine, uracil, and thiouracils towards lead.…”

Conformational, electronic and antioxidant properties of lucidone, linderone and methyllinderone: DFT, QTAIM and NBO studies

“…The three functionals are considered to perform well in describing metal-organic complexes [33][34][35][36][37][38][39]. All calculations were performed with the 6-311 + G(d,p) basis set, which is a Wachters-Hay basis set including diffuse functions [40,41] and is suitable for description of first row transition metal elements.…”

Hydration Energies of Protonated and Sodiated Thiouracils

“…Because of the important role that proton transfer and metal binding to nucleobases can play in their tautomerization [11–14], much effort has gone into investigating the gas-phase proton and alkali metal ion affinities of thiouracils [8, 15–18], and their interaction with cations such, as Ca 2+ [19], Cu + [20], Cu 2+ [21, 22], Cd 2+ [23], or Pb 2+ [24]. Lamsabhi et al [15] measured the gas-phase proton affinities of 2-thiouracil, 4-thiouracil, and 2,4-dithiourcil by Fourier transform ion cyclotron resonance mass spectrometry, and calculated the stabilities of their tautomeric forms.…”